Recently, much progress has been made in increasing the brightness of light emitting diodes (LEDs). As a result, LEDs have become sufficiently bright and inexpensive to serve as a light source in for example illumination arrangements such as lamps with adjustable color. By mixing differently colored LEDs any number of colors can be generated, e.g. white. An adjustable color lighting system is typically constructed by using a number of primary colors, and in one example, the three primaries red, green and blue are used. The color of the generated light is determined by which of the LEDs that are used, as well as by the mixing ratios. To generate “white”, all three LEDs have to be turned on.
In for example industrial and consumer products, high power LEDs are used for replacing traditional incandescent light bulbs in applications such as automotive, industrial, backlight display, and architectural detail lighting systems. However, the high power LEDs suffers from a high thermal load when used in traditional lighting applications. Important parameters of the LED such as efficiency, lifetime, and color are very sensitive to the temperature of the LED, thus making thermal management a key issue in LED lighting applications, especially in adjustable color lighting system where color control is essential for providing a useful application. Of course the same counts for white LEDs, such as for example different types of phosphor coated LEDs.
A popular way of conducting heat management, to reduce the thermal load, is to mount the LEDs on a printed circuit board (PCB), and equip the PCB with a heat sink or dedicate a portion of a metal layer of the PCB for such purpose. This type of cooling arrangement is often bulky since the heat sink needs to be quite large to provide the necessary cooling to the LED. By adding a fan blowing air at the heat sink a smaller heat sink can be used. However, the fan will consume extra power and will often add unwanted noise to the lighting arrangement.
Additionally, fans are subject to wear, limiting their lifetime and reliability. Furthermore, the large bulky structure hampers the design of elegant and sleek lighting applications. A more effective and sleeker cooling arrangement involving a cooling apparatus with an electrostatic flow modifier is presented in patent application US 2007/0002534. The flow modifier is provided for directing an airflow from a fan for providing increased heat transfer from a device surface onto which the flow modifier is arranged. However, not even the cooling arrangement of the cited patent application will solve the problem of getting rid of the bulky fan.
Hence, there is a need for an improvement in relation to the cooling of a device, and more specifically that overcome or at least alleviates the prior art problems of bulky cooling components.